The present invention relates to electrical resistance welding of hydroformed metal tubing with metal sheet for assembling automotive structures.
Recent developments in metal forming technology have permitted the manufacture of automotive vehicle frames and other support members using hydroformed metal tubes. Hydroformed tubes are attractive for automotive vehicles because they afford lightweight and high integrity structures. In many applications, it is desirable to weld such tubes to sheet metal. However, in some instances, the closed nature of such hydroformed tubes imposes practical constraints on localized welding. Conventional spot welding may be employed. However, to improve process efficiency, particularly where selective control over weld nugget formation is desired, and to extend the useful lives of electrodes, there is a need for techniques alternative to conventional spot welding for achieving high integrity localized welding of hydroformed metal tubes to sheet metal.
The present invention provides an improved method for electrical resistance welding a hydroformed metal tube with a metal sheet to make an automotive vehicle structure. A hydroformed metal tube is contacted with a protrusion pattern that has been formed on the metal sheet. The protrusion pattern is defined by a plurality of generally circular and concentric protrusions having triangular cross sections. Using resistance welding electrodes, a portion of the tube is flexed for contacting the outermost protrusion of the pattern. While the tube is in the flexed state, an electrical current is applied to initiate melting from the outermost concentric protrusions radially inward. Upon solidification, a weld nugget results having an outside diameter approximating the outside diameter of the protrusion pattern. The present invention thus meets the need in the art for an improved welding technique affording selective control over nugget formation, reduced energy consumption and prolonged electrode life.
These and other aspects and advantages of the present invention will become apparent upon reading the following detailed description in combination with the accompanying drawings.